I. Field of the Invention
The present invention relates to liquid level sensors such as are mounted though the side wall of a liquid container, referred to as side mount liquid level sensor assemblies.
II. Description of Prior Art
To monitor liquid level in a liquid container, Such as an automobile coolant overflow reservoir or windshield washer tank, it has been the practice to provide a liquid level sensor mounted to the container. The sensor includes a rod-like member or stem about which a float moves depending upon the liquid level in the container. A reed switch is held to the sensor with a magnet attached to the float moving towards and away from the switch to activate and deactivate the switch. Gaining in popularity arc so-called side mount liquid level sensor assemblies which are mounted through the sidewall of the container such that the stem is held in a horizontal disposition. The reed switch is mounted inside the stem and the float moves vertically relative to the stem to bring a magnet held by the float vertically towards or away from the reed switch.
One side mount liquid level sensor assembly which has met with good success is shown in U.S. Pat. Nos. 5,581,062 and 5,742,999, assigned to the assignee hereof, and the disclosures of both of which are incorporated herein by reference in their entireties. In the liquid level sensor assembly there-shown, a switch housing is provided having a rod-like member extending between a mount end and an enlarged disk end, with the mount end adapted to be secured through the sidewall of a liquid container to hold the rod-like member in a generally horizontally disposition in the container. A float, referred to as a buoyant member, has a slot extending vertically therethrough between an open end and an oppositely disposed closed end. The rod-like member is received in the slot of the buoyant member such that the buoyant member can move vertically as the liquid level in the container varies. The open end of the slot is sized to normally receive the rod-like member therethrough and limit structure comprising arms on the buoyant member adjacent the open end and wings formed on the adjacent sidewalls of the rod-like member cooperate to normally prevent the float from falling away from the rod-like member.
In order to mount the float to the housing, the float is oriented at a ninety degree angle relative to the rod-like member such that the slot may pass over the wings and rod from the side. Thereafter, the float is rotated ninety degrees to bring the arms into confronting relationship with the wings to thereby prevent the float from coming away from the housing. This method of assembly has provided great advantages in the manufacture of the liquid level sensor assembly.
The foregoing notwithstanding, some situations have been encountered in which the switch does not work properly. In particular, the float is free to move vertically over a range of travel between two positions, one where the closed end of the slot is against the rod-like member (with the limit structures spaced apart) and one where confronting surfaces of the limit structures engage. The float moves to and between these positions as the fluid level in the container changes, thereby causing the magnet to move towards and away from the reed switch. The range of travel in the above-described device is about 1/4 inch (or 6 mm). In some instances, it has been found that the switch does not reliably change state over that range of float travel.